Use /<auth-type> endpoint to get all authentications

To get all the keys present in Kong, the approach currently being used is:

for_each consumer {
 GET /consumers/:consumer_id_or_name/<auth-type>
}

Recently in Kong, a number of endpoints have been added to auth plugins to ease This will make the process of getting all the keys much more efficient!

To not break things with different Kong versions out there, internally we could hit GET /<auth-type>, if a 404 is returned then we fall back on the iteration approach, but if we get a 200 then, we're good.

Thoughts?